The IBM 1400 series are second-generation (transistor) mid-range business decimal computers that IBM marketed in the early 1960s. The computers were offered to replace tabulating machines like the IBM 407. The 1400-series machines stored information in magnetic cores as variable-length character strings separated on the left by a special bit, called a "wordmark," and on the right by a "record mark." Arithmetic was performed digit-by-digit. Input and output support included punched card, magnetic tape, and high-speed line printers. Disk storage was also available.

Many members of the series could be used as independent systems, as extensions to IBM punched-card equipment, or as auxiliary equipment to other computer systems. Some, however, were intended for specific applications or were economical only as independent systems.

The 1401, announced on October 5, 1959, is the first member of the IBM 1400 series. It was the first computer to deploy over 10,000 units. The IBM 1410 has a similar design, but with a larger address space. The IBM 1460 is logically, but not physically, identical to a 1401 with all of the options, with 16,000 characters of memory, and twice as fast. The 1240 is a banking system, equivalent to the 1440 system with MICR support. The IBM 7010 is logically, but not physically, identical to a 1410, and twice as fast.

Members of the 1400 series include:

Peripherals used with 1400 series machines included:

IBM provided several models compatible (or nearly so) with the 1401.

Honeywell's Honeywell 200 provided approximate 1401 compatibility through a combination of architectural similarity and software support.

With the 1400 series, the smallest addressable unit in core-storage is called a character. The 1400 stores alphameric characters internally in binary-coded decimal (BCD) form, spanning six bits called BA8421. When the character is an operation code or is the first character in a field, another bit, called the "word mark", is included. An odd parity bit, called "C", is also included.